CT-MRI

Coronary CTA

3D Interpretation in Five Minutes

Modern CT scanners are now capable of performing CT coronary arteriography (CTCA) using low intravenous contrast volumes with imaging completed in a less than 10 seconds. However, the issues of success are not so dependent on the actual image acquisition, but in the interpretation by the imaging specialist. A rapid method to navigate through the large 'volumetric' CT dataset involves knowing how to best visualise the various epicardial segments and having a standardised method of review.

John Rumberger and Tony DeFrance, two cardiac experts who specialise in providing CTA certification training, agree that CTAs can be accurately read in a 5-15 minute time span. A normal study can be read and reported in three to five minutes. A study of a patient with a bypass condition and complicated anatomy can take 15 minutes. Dr Rumberger is Director of Cardiac Imaging at the Princeton Longevity Centre in Princeton, NJ. Dr DeFrance is Programme Training Director for the SCCT and Medical Director for CVCTA Education in San Francisco, CA. Both use a consistent cardiac protocol using 'vessel navigation' to read CTAs. "The choice of a visualisation workstation is one of the most important decisions to be made by physicians working with CTCA," says Dr Rumberger.

"The major concern is that the reading/ interpretation platform must provide for rapid review of the huge 2-D and 3-D volume datasets and convenient structuring of the final report. The system must offer the ability to perform advanced image manipulation and the potential to review dynamic imaging sequences for determining cardiac dimensions and volumes (such as with left ventricular size and global/ regional function). Finally, the workstation should have a universal operating system so that further image processing (eg for formal presentations and research papers), image storage and communication (eg via a server or the PACS system) and report generation and distribution to referring physicians can be done easily and seamlessly. I use the TeraRecon Aquarius Workstation for these and other cardiac and Coronary CTA. "The interpretation protocol should proceed along established guidelines for interpreting tomographic images and in a systematic

fashion. My work path of how I approach CTCA of the native coronary arteries starts with the Left Main (LM) and then goes down the Left Anterior Descending (LAD). Once I review the LAD, I return to the LM and proceed down the Left Circumflex (LCX) and its branches. Finally, I return to the Right Coronary Artery (RCA) ostium, and proceed distally to the most inferior segments," he said.

Dr Rumberger's protocol includes reviewing six different phases of the heart cycle, several end systolic views of 45-50 per cent and several around the 70 per cent phase. "Even though I may not use all the phases, I need to quickly establish the best set of images to review. Dr DeFrance reads in a similar and consistent fashion. After an initial evaluation of the 3D image looking for abnormalities, he opens a coronal MIP image to assess study quality and to identify artifacts. He then looks at non-coronary artery structures in a stepwise fashion. To evaluate coronary arteries, Dr DeFrance uses centerline analysis, oblique rotation, and curved planar reformat techniques. "There is so much data in these studies that if you are not trained to read in a systematic and stepwise fashion, you can miss pathology and misdiagnose patients," said Dr DeFrance. He believes that establishing your work-flow patterns early on is essential to building confidence and speed which in turn leads to better patient care.

When it comes to reviewing large CTA datasets, not all workstations are created equal. Many workstations are unable to load all phases of the CTA study into active memory. It is essential for accurate diagnosis that a workstation support fast loading of all the ECG-phases as well as interactive switching between them during diagnostic review.

TeraRecon's Aquarius Workstation employs both, a software and unique hardware solution (VolumePro board) to manage large CTA datasets with the ability to seamlessly (and in a straightforward manner) page through the phases at any given anatomic site to arrive at the one which represents the least or absent motion artifact.

Contact: Nehal Shah
nehal@terarecon.com
Mobile: 9920592475